The present invention relates to a multifunction acoustic device used in a portable instrument such as a portable telephone.
There has been provided an acoustic device of the portable instrument in which a speaker is provided for generating sounds of calling signals, and a vibrating motor is provided for informing the receiver of calling signals without generating sounds. In such a device, since both of the speaker and the motor are mounted in the device, the device is increased in size and weight, and in manufacturing cost.
In recent years, there is provided a multifunction acoustic device in order to remove the above described disadvantages. The multifunction acoustic device comprises a speaker having a vibrating plate and a permanent magnet magnetically connected to a voice coil mounted on the vibrating plate of the speaker. The permanent magnet is independently vibrated at a low frequency of 100-150 Hz so as to inform the receiving of calling signals by the vibration of the case of the device, which is transmitted to the body of the user of the device.
FIG. 9 is a sectional view of a conventional electromagnetic induction converter disclosed in Japanese Utility Model Application Laid Open 5-85192. The converter comprises a diaphragm 506 mounted in a case 512 at a periphery thereof, a voice coil 508 secured to the underside of a central portion 507 of the diaphragm 506, a spring plate 511 mounted in the case 512, and a permanent magnet 510 secured to a central portion of the spring plate 511, inserted in the voice coil 508.
By applying a low or high frequency signal to the voice coil 508, the spring plate 511 is vibrated in the polarity direction Y of the magnet 510.
In the device, the diaphragm 506 and the spring plate 511 are relatively moved through the magnetic combination between the voice coil 508 and the magnet 510. Consequently, when a low frequency signal or a high frequency signal is applied to the voice coil 508, both of the diaphragm 506 and the spring plate 511 are sequentially vibrated. As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, vibrating both of the voice coil 508 and the magnet 510 causes the low frequency vibration of the magnet to superimpose on the magnetic combination of the voice coil 508 and the magnet 510, which further largely distorts the sounds.
FIG. 10 is a sectional view showing a conventional multifunction acoustic device. The device comprises a speaker vibrating plate 603 made of plastic and having a corrugated periphery 603a and a central dome, a voice coil 604 secured to the underside of the vibrating plate 603 at a central portion, and a magnet composition 610. The vibrating plate 603 is secured to a frame 609 with adhesives.
The magnetic composition 610 comprises a lower yoke 605, a core 601 formed on the yoke 605 at a central portion thereof, an annular permanent magnet 602 mounted on the lower yoke 605, and an annular upper yoke 606 mounted on the permanent magnet 602. The lower yoke 605 and the upper yoke 606 are resiliently supported in the frame 609 by spring plates 607 and 608. A magnetic gap 611 is formed between a periphery 601a of the core 601 and an inside wall 606a of the upper yoke 606 to be magnetically connected to the voice coil 604.
When an alternating voltage is applied to the voice coil 604 through input terminals 612a and 612b, the speaker vibrating plate 603 is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil 604, the speaker vibrating plate 603 and the magnetic composition 610 are sequentially vibrated, since the magnetic composition 610 and the speaker vibrating plate 603 are relatively moved through the magnetic combination of the voice coil 604 and the magnet composition 610.
As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, the driving of both the voice coil 604 and the magnetic composition 610 causes the low frequency vibration to superimpose on the magnetic combination of the voice coil 604 and the magnetic composition 610, which further largely distorts the sounds.
FIG. 11 is a sectional view showing another conventional multifunction acoustic device. The device comprises the speaker vibrating plate 603 made of plastic and having the corrugated periphery 603a and the central dome, the voice coil 604 secured to the underside of the vibrating plate 603 at a central portion, and the magnet composition 610. The vibrating plate 603 is secured to the frame 609 with adhesives.
The magnetic composition 610 comprises a lower yoke 703, core 601 formed on the yoke 703 at a central portion thereof, an annular permanent magnet 702 secured to the lower yoke 703, and annular upper yoke 606 having a peripheral wall 606b and mounted on the permanent magnet 702. The upper yoke 606 is resiliently supported in the frame 609 by spring plates 707 and 708. A first magnetic gap 701 is formed between the periphery 601a of the core 601 and the inside wall 606a of the upper yoke 606 to be magnetically connected to the voice coil 604. A second gap 705 is formed between a periphery 703a of the lower yoke 703 and inside wall 606a of the upper yoke 606. A driving coil 706 is secured to the frame and inserted in the second gap 705.
When an alternating voltage is applied to the voice coil 604 through input terminals 612a and 612b, the speaker vibrating plate 603 is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil 604, the speaker vibrating plate 603 and the magnetic composition 610 are sequentially vibrated, since the magnetic composition 610 and the speaker vibrating plate 603 are relatively moved through the magnetic combination of the voice coil 604 and the magnet composition 610.
When a high frequency signal for music is applied to the voice coil 604, only the speaker vibrating plate 603 is vibrated. Therefore, there does not occur distortion of the sound. Furthermore, when a low frequency signal is applied to the driving coil 706, only the magnetic composition 610 is vibrated, and the speaker vibrating plate 603 is not vibrated.
However if a high frequency signal is applied to input terminals 612a, 612b, and a low frequency signal is also applied to input terminals 704a, 704b, the speaker vibrating plate 603 and magnetic composition 610 are sequentially vibrated, thereby reducing the sound quality.
In the above described conventional devices, both the speaker vibration plate and the magnetic composition are vibrated when a low frequency signal or a high frequency signal is applied to the voice coil. This is caused by the reason that the low frequency vibrating composition is vibrated in the same direction as the high frequency vibrating direction.
An object of the present invention is to provide a trouble shooting for the multifunction acoustic device which may deal with trouble such as the stopping of a rotor by shock applied to the device.
According to the present invention, there is provided a multifunction acoustic device comprising a frame, a rotor rotatably supported in the frame, a stator provided in the frame, a permanent magnet provided on the rotor, a diaphragm supported in the frame, a coil for forming magnetic fluxes between the rotor and the stator, voltage detecting means for detecting a voltage generating at the coil, comparing means for comparing a voltage detected by the voltage detecting means in the operation of the acoustic device with a reference voltage which corresponds to a voltage generating at abnormal rotation of the rotor and for producing an abnormal signal when the detected voltage is equal to or higher than the reference voltage, speed control means responsive to the abnormal signal for starting to rotate the rotor from a low speed.
The reference voltage is a voltage which corresponds to a voltage when the rotor starts to rotate at a low speed.
The abnormal rotation is the stopping of the rotation of the rotor.
The speed control means sets the speed of the rotor at the starting of the rotation and at a constant speed during the sound generating condition.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.